pnmdepth
Change color depth of PNM images
TLDR
Change image depth
$ pnmdepth [newdepth] [input.pnm] > [output.pnm]
Reduce to 8-bit$ pnmdepth 255 [input.pnm] > [output.pnm]
Reduce to 4-bit$ pnmdepth 15 [input.pnm] > [output.pnm]
SYNOPSIS
pnmdepth newmaxval [file]
DESCRIPTION
pnmdepth changes the maximum sample value (color depth) of PNM images by proportionally rescaling all pixel values. For example, converting from maxval 65535 (16-bit) to 255 (8-bit) scales each sample value accordingly.
This is useful for reducing file size by lowering bit depth or for ensuring compatibility with tools that expect specific depth values. Part of the Netpbm toolkit; superseded by pamdepth.
PARAMETERS
NEWMAXVAL
New maximum sample value (depth).FILE
Input PNM file.
CAVEATS
Values are scaled proportionally. Part of Netpbm suite.
HISTORY
pnmdepth was created as part of Netpbm for image depth conversion.